The present invention relates to improved processes systems plant and related product for hydrolysing and making use of hydrolysed lignocellulosic materials.
Most scientists know that many very valuable products can be made from plant fibre pulp prepared by a laboratory method known as "explosion hydrolysis". Unfortunately; in order to get $1 worth of these products, one must spend most of that $1 on heat energy and other costs. Huge amounts of research money have been applied world-wide in the quest for a commercially viable process with little success.
"Explosion" hydrolysis consists of placing a charge of wood chips or similar cellulosic materials into a strong, closed pressure vessel in order to bring a thermochemical modification. High pressure steam is passed through the material for a specified time, according to temperature. At the end of the steaming period a valve on the bottom of the vessel is opened and the hydrolysed material is "exploded" out of the vessel. What comes out of the vessel is a rather soggy, very hot, wet substance which is ready to be processed so as to utilise the various chemicals which have been liberated by the hydrolysis.
In its simplest form, explosion hydrolysis is carried out without any chemicals or additives but catalysts can be used. Explosion hydrolysis was used extensively in Germany during the war period when the shortage of chemicals meant that the economic considerations were over-ridden by a desperate need for the end products. A tremendous resurgence of interest in explosion hydrolysis also arose during the early 1970's when the costs of petro-chemicals began to sky-rocket. Large numbers of new projects were initiated at that time when it was thought that explosion hydrolysis would be rendered more competitive. With the recession in oil prices the projects were abandoned.
There is no doubt as to the value of hydrolysed ligno-cellulose fibre, but up until now, its use has been totally circumscribed in the absence of an economic, large scale production method. There has been absolutely no interest in the production of the valuable substances found in bio-mass because of a total concentration and reliance on petro-chemical. Strong incentives to increase biomass plantings in order to reverse the carbon dioxide balance coincides with the emergence of this new technology.
There is no real substitute for the use of heat in the process of hydrolysis of lignocellulosic material and the laws of thermo-dynamics ensure that there are not short-cuts as to the amount of heat which is required. The reason that the process has been uneconomic in the past is that it has been possible to use the heat only once and, at the end of each cycle, the heat has almost been totally lost to the atmosphere.
[Explosion hydrolysis was very widely practiced in the 1930's and right up to the present day to produce hardboard by the Masonite process. The practice has almost completely disappeared and been replaced by more efficient methods. Hardboard made by the Masonite process was bonded entirely with natural resins produced by the process and no synthetics were used. Unfortunately, 100 tonnes of water were needed for every one ton of fibre produced which brought enormous pollution problems].
The present invention provides a totally different apparatus in which the hydrolysis preferably proceeds within a continuous energy re-circulation system where there is a minimum of waste. Even surplus heat is available in a valuable form. The innovation represents an enormous break-through where an old, well known but previously uneconomic process has been brought into the space age. The immensely efficient, pollution-free energy system is economically competitive, no matter how low oil prices sink, making woody plant fibre biomass a certain alternative as a chemical feed material.
It is an object of the present invention therefore to provide an alternative to prior art processes, systems plant.
Accordingly in one aspect the present invention consists in a process for preparing a hydrolysed lignocelluiosic material substantially devoid of available water from a source of lignocellulosic material, said process comprising the steps of;
start up preparing a hydrolysis system for an input of lignocellulosic material by a heat exchange energy build up and water injection to provide a primary system having a hydrolysing zone of a circulating stream of saturated steam under elevated pressure and temperature,
introducing into the circulating stream once hydrolysis conditions are attained for the desired hydrolysis, a feed of lignocellulosic material to be carried as being hydrolysed in the circulating saturated steam stream to an outlet zone of the primary system,
thereafter passing from the outlet of the primary system the still heated solids stream of lignocellulosic material that has been at least substantially hydrolysed into a secondary system having a circulating hydrolysing zone of superheated steam, the passing of the solids stream between the systems resulting in the flashing off of at least some moisture at a reduced pressure to that of the primary system as the hydrolysis continues to some extent,
and at a desired dryness extracting and/or using the solids stream from the secondary system,
the process being additionally characterised in that there is a substantially constant heat exchange input into the primary system at least after start up and the adjustment of the saturated steam conditions within the primary system is by a control of the solids input (if the solids are moist), control of any further water injection into the primary system, and a control of steam bled as an energy outlet from the primary system, and being further characterised that there is no substantial free passage of saturated steam from the primary system into the superheated steam zone of the secondary system.
Preferably the passing of lignocellylosic material from the primary system to the secondary hydrolysing system is by means of an auger or screw controllable as to speed of rotation, the speed of which is finally determinative of the period of time under which solids material injected into the primary system is subjected to the hydrolysing conditions of the primary system.
Preferably the primary system is used as an energy source for attaining and/or maintaining at least in part the temperature of the secondary system.
Preferably said secondary system in use is heated solely by steam bled from the primary system and the heat of the solids stream.
Preferably the feed to said auger or screw is from the base of a cyclone.
Preferably the feed from the auger or screw is through a pressure reducing system into said secondary system adapted to minimise loss of saturated steam of the primary system.
Preferably said solids stream is taken from a cyclone of the secondary system.
Preferably said solids stream taken from the secondary system is pressed at a suitable temperature and pressure into a self polymerising form.
Preferably the circulating zone of each of the primary and secondary systems involves the use in each of at least one fan.
In a further aspect of the present invention consists in, in a two stage system for hydrolysing lignocellulosic material where hydrolysis is performed using a saturated steam carrier for the lignocellulosic material in a first stage hydrolysis system and continues into a second stage using a superheated steam carrier, a method of energy control in the system which comprises:
(a) building up energy in the first stage hydrolysis system using heat exchange transfer into the system.
(b) only once sufficient energy has been introduced into the first stage hydrolysis system commencing the controlled hydrolysis of the lignocellulosic material only then being introduced while introducing into the hydrolysis system sufficient energy via heat exchange means and water (in the lignocellulosic material or otherwise) to maintain the system in a substantially steady state while excess steam is being bled from the hydrolysis system and as the solids material is removed after having been subjected to the hydrolysing conditions for a desired time, and
(c) providing or at least maintaining the superheated steam carrier in the second stage system by flashing steam from the moisture of the substantially hydrolysed lignocellulosic material as it is transferred from the first stage hydrolysis system to the second stage hydrolysis system, the superheated steam of the second system being maintained as superheated steam by heat exchange and a bleeding of excess superheated steam from the second stage system as the substantially dry hydrolysed material is removed therefrom.
Preferably the heat exchange of said second stage hydrolysis system is with steam bled from the first stage hydrolysis system.
Preferably excess steam bled from the first stage hydrolysis system beyond that used for heat exchange of said second stage hydrolysis system is deployed elsewhere as a usable steam source.
Preferably the dry cellulosic material obtained as a product is at least in part pressed into a self polymerising form under a suitable pressure and temperature.
In still a further aspect the present invention consists in plant which in use can perform a process for preparing a hydrolysed lignocellulosic material substantially devoid of available water from a source of lignocellulosic material, said process comprising the steps of;
start up preparing a hydrolysis system for an input of lignocellulosic material by a heat exchange energy build up and water injection to provide a primary system having a hydrolysing zone of a circulating stream of saturated steam under elevated pressure and temperature,
introducing into the circulating stream once hydrolysis conditions are attained for the desired hydrolysis, a feed of lignocellulosic material to be carried as being hydrolysed in the circulating saturated steam stream to an outlet zone of the primary system,
thereafter passing from the outlet of the primary system the still heated solids stream of lignocellulosic material that has been at least substantially hydrolysed into a secondary system having a circulating hydrolysing zone of superheated steam, the passing of the solids stream between the systems resulting in the flashing off of at least some moisture at a reduced pressure to that of the primary system as the hydrolysis continues to some extent,
and at a desired dryness extracting and/or using the solids stream from the secondary system,
the process being additionally characterised in that there is a substantially constant heat exchange input into the primary system at least after start up and the adjustment of the saturated steam conditions within the primary system is by a control of the solids input (if the solids are moist), control of any further water injection into the primary system, and a control of steam bled as an energy outlet from the primary system, and being further characterised that there is no substantial free passage of saturated steam from the primary system into the superheated steam zone of the secondary system, said plant comprising;
a primary hydrolysis plant having a circulatory hydrolysis zone to operate at an elevated pressure and temperature, an inlet for lignocellulosic solids, a controllable water injection means into said zone, a bleed off valve for excess steam from said zone, a solids outlet, fan means to cause a circulatory movement of steam in said zone and entrainment of the lignocellulosic solids in the stream from the inlet thereof to an outlet, and a cyclone to gravity accumulate the solids at the outlet,
a secondary hydrolysis plant having a circulatory hydrolysis/drying zone to operate at a lower pressure than the primary hydrolysis zone, an inlet to receive into the hydrolysis/drying zone the solids from the outlet of said primary zone, an outlet for superheated steam, a solids outlet, fan means to cause a circulatory movement of steam in said zone and entrainment of the solids in the stream from the inlet to said zone to the solids outlet, and a cyclone to gravity direct the solids to the outlet,
an auger or screw including means controllable as to speed of rotation to feed solids materials between the outlet of the primary zone to the inlet of the secondary hydrolysis plant without a substantial passage of saturated steam from the first zone,
heat exchange means for heating said primary zone,
heat exchange means for heating said secondary hydrolysis plant,
and means to control as required for the process to be performed the dwell time of solids and steam conditions in at least the primary plant.
Preferably at least some of the steam released from the primary hydrolysis plant by said bleed off valve provides a heat input to said heat exchange means for heating said secondary hydrolysis plant.
Preferably said means to control dwell time and steam conditions controls the plant such that it performs a process whereby there can be an energy control in the system whereby there is;
(a) on start up a building up of energy in the primary hydrolysis system using said heat exchange means thereof,
(b) only once sufficient energy has been introduced into the primary hydrolysis system commencing the controlled hydrolysis of the lignocellulosic material only then being introduced while introducing into the primary hydrolysis system sufficient energy via said heat exchange means of the primary hydrolysis system and water (in the lignocellulosic material or otherwise) to maintain the system in a substantially steady state while excess steam is being bled from the hydrolysis system and as the solids material is removed after having been subjected to the hydrolysing conditions for a desired time,
(c) providing or at least maintaining the superheated steam carrier in the secondary hydrolysis system by flashing steam from the moisture of the substantially hydrolysed lignocellulosic material as it is transferred from the primary hydrolysis system to the secondary hydrolysis system, the superheated steam of the second system being maintained as superheated steam by the heat exchange means of the secondary plant and a bleeding of excess superheated steam from the secondary system, and
(d) removing substantially dry hydrolysed material from the secondary system.
Preferably said auger or screw including means includes a device to minimise the substantial passage of saturated steam from the primary hydrolysis zone into the secondary hydrolysis plant, such apparatus comprising;
means defining a chamber having an inlet port and an outlet port,
a first valving element disposed in said chamber movable to open or close said inlet port,
a second valving element disposed in said chamber movable to open or close said inlet port,
means whereby said valving element can be caused to move as required,
the construction and arrangement being such that in use solids from the primary zone under a fluid pressure can enter said chamber via the inlet port while said outlet port is closed and the inlet port is closed before the outlet port is opened to allow said solids under the fluid pressure of the primary zone to egress therefrom into the secondary hydrolysis zone.
In yet a further aspect the present invention consists in a formed product created from a self polymerising hydrolysed lignocellulosic material under a form creating pressure and temperature wherein said hydrolysed lignocellulosic material has been prepared by a process for preparing a hydrolysed lignocellulosic material substantially devoid of available water from a source of lignocellulosic material, said process comprising the steps of;
start up preparing a hydrolysis system for an input of lignocellulosic material by a heat exchange energy build up and water injection to provide a primary system having a hydrolysing zone of a circulating stream of saturated steam under elevated pressure and temperature,
introducing into the circulating stream once hydrolysis conditions are attained for the desired hydrolysis, a feed of lignocellulosic material to be carried as being hydolysed in the circulating saturated steam stream to an outlet zone of the primary system,
thereafter passing from the outlet of the primary system the still heated solids stream of lignocellulosic material that has been at least substantially hydrolysed into a secondary system having a circulating hydrolysing zone of superheated steam, the passing of the solids stream between the systems resulting in the flashing off of at least some moisture at a reduced pressure to that of the primary system as the hydrolysis continues to some extent,
and at a desired dryness extracting and/or using the solids stream from the secondary system,
the process being additionally characterised in that there is a substantially constant heat exchange input into the primary system at least after start up and the adjustment of the saturated steam conditions within the primary system is by a control of the solids input (if the solids are moist), control of any further water injection into the primary system, and a control of steam bled as an energy outlet from the primary system, and being further characterised that there is no substantial free passage of saturated steam from the primary system into the superheated steam zone of the secondary system.
In still a further aspect the present invention consists in a formed product created from a self polymerising hydrolysed lignocellulosic material under a form creating pressure and temperature wherein said hydrolysed lignocellulosic material has been provided from a two stage system for hydrolising lignocellulosic material where hydrolysis is performed using a saturated steam carrier for the lignocellulosic material in a first stage hydrolysis system and continues into a second stage using a superheated steam carrier, wherein there was performed a method of energy control in the system which comprises:
(a) building up energy in the first stage hydrolysis system using heat exchange transfer into the system,
(b) only once sufficient energy has been introduced into the first stage hydrolysis system, commencing the controlled hydrolysis of the lignocellulosic material which is only then introduced, while introducing into the hydrolysis system sufficient energy via heat exchange means and water (in the lignocellulosic material or otherwise) to maintain the system in a substantially steady state while excess steam is being bled from the hydrolysis system and as the solids material is removed after having been subjected to the hydrolysing conditions for a desired time, and
(c) providing, or at least maintaining, the superheated steam carrier in the second stage system by flashing steam from the moisture of the substantially hydrolysed lignocellulosic material as it is transferred from the first stage hydrolysis system to the second stage hydrolysis system, the superheated steam of the second system being maintained as superheated steam by heat exchange and a bleeding of excess superheated steam from the second stage system as the substantially dry hydrolysed material is removed therefrom.
Preferably the product of either of the preceding two paragraphs is a board or panel.